Synovial sarcoma is a soft tissue tumor of the joints that affects young adults. It is characterized by a chromosomal translocation t(X; 18;pl 1;ql 1) that juxtaposes the SYT gene on chromosome 18 and the SSX gene on the X chromosome, resulting in the fusion, SYT-SSX. In the cancer, SYT-SSX is thought to exert a dominant gain of function, while the wt SYT allele is significantly down regulated, leading to loss of SYT normal function. a-catenin is the mediator of the wnt pathway, an active program in development and cancer. We found that SYT associates with beta-catenin in the nucleus and appears to suppress its function, while SYT-SSX activates it. The objective of this proposal is to characterize the functional relationship between SYT and beta-catenin, and its deregulation by SYT-SSX, in adult tissue and development. In addition, we will identify the nuclear components involved in this process and their role in mediating SYT and SYT-SSX effects on a-catenin. The aim of this research proposal is to help gain a clearer understanding of synovial sarcoma development.